1. Field of the Invention
The present invention relates to a recording medium for formation of a print having texture and image quality comparable to silver salt photographs by application of droplets of a recording liquid such as an ink, especially a recording medium suitable for image formation by ink-jet recording. The present invention also relates to a process for producing the recording medium, and an image-forming method employing the recording medium.
2. Related Background Art
The ink-jet recording method conducts recording by projecting fine droplets of a recording liquid such as an ink to deposit the droplets onto a paper sheet or a like recording medium to record an image or letters. The ink-jet recording method has advantages of high printing speed, low noise generation, ease of multicolor printing, flexibility of the recording pattern, needlessness of image development, and so forth. Therefore, the ink-jet recording methods and apparatuses are being developed and becoming widespread not only as printers but also as output devices of information apparatuses such as copying machines, word processors, and plotters. Recently, digital cameras, digital videos, scanners, and the like of high-performance are commercialized at low prices. As the results of the widespread use of the above apparatuses and popularization of personal computers, ink-jet type printers have come to be used suitably. Under such a background, the ink-jet recording is demanded which is capable of readily outputting images comparable to the multicolor print images formed by silver salt photography or gravure printing.
To meet such needs, the structure of the printer and the method of the recording are being improved for higher printing speed, higher fineness of the printed image, and full color printing. The recording medium used therefor is also being improved in terms of the properties and characteristics thereof.
Various ink-jet recording mediums are disclosed hitherto. For example, Japanese Patent Application Laid-Open No. 52-9074 discloses a recording medium having an ink-receiving layer containing a silica type pigment having a large specific surface area as the main components and having voids to improve the ink absorbing rate. Japanese Patent Application Laid-Open No. 63-22997 discloses a recording medium having adjusted voids in the pigment layer for constituting an ink-receiving layer. Japanese Patent Application Laid-Open Nos. 55-51583 and 56-157 disclose incorporation of powdery amorphous silica into the ink-receiving layer to increase the ink absorbency of the ink-receiving layer to obtain printed dots with high printing density without ink running.
Alumina hydrate is attracting attention in recent years as the material for constituting the ink-receiving portion of the recording medium. This is because the alumina hydrate, which is in a state of fine particles having a positive charge, is capable of fixing the dye of the ink and forming a transparent layer to give images with high color-developability and high water resistance. Such recording mediums are disclosed, for example, in Japanese patent Application Laid-Open Nos. 7-232473, 9-66664, and 2-276670. Japanese Patent Application Laid-Open Nos. 9-99627, and 11-286171 disclose respectively a recording medium having an ink-receiving layer constituted of alumina hydrate particles having a specified crystal thickness, or a specified pore structure. Japanese Patent Application Laid-Open No. 10-95754 discloses a recording medium having an ink-receiving layer mainly composed of aggregate of particles of alumina hydrate formed on a paper base such as a wood-free paper sheet other than a plastic film.
Japanese Patent Application Laid-Open No. 11-1060 discloses a recording medium which has an ink-receiving layer constituted of a porous layer containing barium sulfate and a layer containing nonoriented alumina hydrate provided in this order on a base material to raise the ink absorption rate and prevent beading and to achieve excellent print quality. Japanese Patent Application Laid-Open No. 6-79967 discloses a recording medium having a cast-treated layer containing alumina hydrate to achieve simultaneously high ink absorbency and high glossiness of prints. Japanese Patent No. 2686670 discloses a recording medium which has an ink-receiving layer constituted of two layers to achieve higher image density: an upper layer being mainly composed of aluminum oxide having a larger specific surface area and a lower layer being mainly composed of a pigment having a smaller specific surface area. Japanese Patent Application Laid-Open No. 2001-10222 discloses a recording medium which has a lower layer containing barium sulfate and another pigment formed on a supporting member and an upper layer containing aluminum oxide as the main pigment formed thereon.
Various methods are disclosed which improve the recording medium for higher ink absorbency for high printing speed of printers without lowering the high image density. For example, an ink-receiving layer is formed with a pigment having a large pore volume to increase the void volume for absorbing and retaining the ink. Otherwise, an ink-receiving layer is formed from an ink-absorbent polymer material. However, such an ink-receiving layer may give rise to white turbidity of the dots by irregular light reflection or other causes not to give desired high image density or high glossiness. Increase of the coating thickness of the ink-receiving layer for higher ink absorbency will increase the cost of the material and production process.
The glossy recording medium having a paper base material involves a problem of waving of the recording face after ink-jet recording to lower the glossiness. The constitution having a barium-sulfate-containing layer disclosed in the aforementioned Japanese Patent Application Laid-Open No. 11-1060, which can prevent the waving to a certain extent, needs an additional thick ink-receiving layer thereon in order to obtain sufficient ink-absorbency owing to the less ink-absorbency of the barium-sulfate-containing layer.
Still higher surface glossiness is required for obtaining a printed matter comparable to silver salt type photographs. The constitution of the layer containing barium sulfate and another pigment formed on a supporting member disclosed in Japanese Patent Application Laid-Open No. 2001-010222 is still unsatisfactory in surface gloss or other properties.